<template>
	<div>
		<router-link
		tag="div"
		to="/"
		class="header-abs"
		v-show="showAbs"
		>
			<div class="iconfont header-abs-back">&#xe624;</div>
		</router-link>
		<div
		class="header-fixed"
		v-show="!showAbs"
		:style="opacityStyle"
		>
			<router-link to="/">
				<div class="iconfont header-fixed-back">&#xe624;</div>
			</router-link>
			景点详情
		</div>
	</div>
</template>

<script>
export default{
	name: 'DetailHeader',
	data () {
		return {
			showAbs: true,
			opacityStyle: {
				opacity: 0
			}
		}
	},
	methods: {
		handleScroll () {
			console.log('scroll')
			// console.log(document.documentElement.scrollTop) //不兼容，此值一直为0
			// console.log(document.body.scrollTop)
			// console.log(window.pageYOffset)
			const top = document.documentElement.scrollTop || document.body.scrollTop || window.pageYOffset
      if (top > 60) {
        let opacity = top / 140
        opacity = opacity > 1 ? 1 : opacity // 限制top>60后，opacity只能是1
        this.opacityStyle = {
        	opacity: opacity
        }
        this.showAbs = false
      } else {
        this.showAbs = true
      }
		}
	},
	mounted () {
		window.addEventListener('scroll', this.handleScroll)
	},
	destroyed () {
		window.removeEventListener('scroll', this.handleScroll)
	}
}
</script>

<style lang="stylus" scoped>
	@import '~@/assets/styles/varibles.styl'
	.header-abs
		position: absolute
		left: .2rem
		top: .2rem
		width: .8rem
		height: .8rem
		line-height: .8rem
		border-radius: .4rem
		text-align: center
		background: rgba(0, 0, 0, .5)
		.header-abs-back
			color: #fff
			font-size: .4rem
	.header-fixed
		z-index: 2
		position: fixed
		top: 0
		left: 0
		right: 0
		// overflow: hidden
		height: $headerHeight
		line-height: $headerHeight
		text-align: center
		color: #fff
		background: $bgColor
		font-size: .32rem
		.header-fixed-back
			position: absolute
			top: 0
			left: 0
			width: .64rem
			text-align: center
			font-size: .4rem
			color: #fff
</style>